Optical networks provide a means of transporting data for communication purposes. Optical networks generally comprise a set of point-to-point transparent optical nodes connected by a transparent media, e.g. optical fiber or free space; each node comprising a transmitter and a corresponding receiver.
There are two primary advantages in using optical networks rather than electrical networks. A higher bandwidth or data rate is available in optical networks because of the higher carrier frequency. Further, longer communications distances are possible in an optical network because of the low attenuation of fiber optics and/or free space in an optical network can spread over thousands of miles without a need for regeneration, although optical to electrical to optical steps are needed to boost the signal to noise ratio.
In order to increase existing optical network capacity and avoid the need to install more fiber, the technique of Wavelength Division Multiplexing (WDM) has been developed. WDM is a means of increasing the data-carrying capacity of an optical fiber by concurrently transmitting different signals having different wavelengths through the same fiber. This is similar to Frequency Division Multiplexing (FDM) used in the analogous electrical and radio transmission systems. WDM comprises any technique by which two or more optical signals having different wavelengths are simultaneously transmitted in the same direction over one strand of optical fiber and then separated by wavelength at the distant end. Each wavelength can be thought of as a virtual channel, or a light pipe, which can support a given signaling rate.
Other techniques in the area of traffic grouping or wave banding, both for architectural reasons and as a means to reduce the number of ports in optical cross connects wherever different traffic can share the same port are being explored. However, wave banding architectures generally require individual transmitters be assigned to each channel, just as in the case for WDM optical networks.
One major disadvantage in current WDM optical networks is that every optical channel requires its own light source. For example, in a network designed for M bands, each containing N channels, M×N fixed lasers are required as light sources. The necessity of individual light sources increases the cost of providing adequate optical networks, as well as the operational cost of maintaining the networks. For example, there is a high cost associated with the need to inventory and provision the optical network with sources for each optical channel. To partially reduce such inventory and provisioning costs, tunable lasers may be used. However, even using tunable lasers would require one type of laser be inventoried for each channel; e.g. N tunable lasers in the example above.
Therefore, there remains a need in the art for improvements in the provision of light sources for optical networks.